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Johnboy777
Posted on Wednesday, February 03, 2010 - 01:44 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Measuring Exhaust Flow?

I am looking for an inexpensive gadget or a quick and dirty way to measure the flow of my exhaust at 3,000 RPM and at 6,000 RPM, while stationary.

I plan to build a straight-through muffler with a small restrictor plate at the end to match the flow of the stock XB exhaust, which has the valve wired open.

The end product should be louder and allow me to use the same fuel maps, which I have worked on a lot.

Thanks,
John

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Ourdee
Posted on Wednesday, February 03, 2010 - 06:22 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Do the math. 3,000 rpm is 1,500 X 1,203 cc = flow per minute. Then figure the expansion of the gas. I'm too lazy.
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Johnboy777
Posted on Wednesday, February 03, 2010 - 06:51 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

""Do the math. 3,000 rpm is 1,500 X 1,203 cc = flow per minute. Then figure the expansion of the gas. I'm too lazy.""

My bad...perhaps I need to explain it better.

What I am trying to do is establish a baseline for my stock muffler which is wired open.

I then want to tune another straight-through muffler for roughly the same flow.

I plan to more or less match the flow of the stock muffler by restricting the
flow of the straight-through muffler.

I guess you can think of it as a Jardine with a Quiet Module installed.

My question, how do I measure the flow of the stock muffler, to establish a baseline.

I don't have access to a flowbench or a manometer.

Thanks
John

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1324
Posted on Wednesday, February 03, 2010 - 10:02 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Without a flow bench, you're pissing in the wind. That is the best way to quantify flow and pressure drop. Luckily for you, they aren't terribly difficult to build.
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Gbaz
Posted on Friday, February 05, 2010 - 08:57 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Build a manometer to measure the presure dif from the front of the muf to the back.
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Johnboy777
Posted on Friday, February 05, 2010 - 09:23 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

""Build a manometer to measure the presure dif from the front of the muf to the back""

Yeah, that seems to be where I'm heading - I'm thinking off the bike, hooked to
a super duty ShopVac w/ the manometer attached.

Two LINKS for Homemade Manometers:

http://www.komar.org/faq/manometer/

http://www.vfrdiscussion.com/forum/index.php?showt opic=16200

My thought here is some sort of a a jig on the end of the muffler(s) with
the Manometer attached to it.

John
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1324
Posted on Friday, February 05, 2010 - 10:25 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Manometers will essentially give you the same data as a true flow bench. However, keep in mind a basic jig at the outlet will not give you accurate pressure (and hence flow) measurements. Exhaust outlets are very turbulent and depending on exhaust design and engine speed, there will be varying amounts of flow reversion. In this case, you won't be able to get an accurate picture of what is truly going on. You may very well modify a design which appears to flow more but actually just has flow in both directions. I'd recommend a flow bench for the simple fact you can control how the outlet feeds and ensure there is is no/minimal reversion.
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Johnboy777
Posted on Friday, February 05, 2010 - 12:58 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Thanks, 1324 ,that’s exactly the knind of info I was looking for.

Yeah, it’s going be only so accurate (you're right), I’m hoping
I might get it close enough for what I’m doing, though – tuning one muffler
to match another in back pressure at a given air volume.

My thought is that the inlet side would be a constant and the outlet (per each muff.) might
need an identical 3” or 4” pipe of a smaller inside dia. attached to the end of each muffler to try
and keep the outlet runner size fairly consistent between the mufflers. And the 4" run
might help stabilize the exiting airflow, somewhat...just a WAG, on my part, though.

I feel like I might be missing the whole velocity vs. volume thing here.



EDIT:
What's that old saying - to the ignorant there are many possibilities, to the master
there is only one....very funny.

.

(Message edited by johnboy777 on February 05, 2010)
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Johnboy777
Posted on Friday, February 05, 2010 - 01:17 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

BTW, here's the muffler I going to start with:

MagnaFlow 10445 (2.25in. Inlet/ 2.25in. Out)
http://www.summitracing.com/parts/MPE-10445/?rtype =10
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Pogue_mahone
Posted on Friday, February 05, 2010 - 11:50 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

hey john
i had a jardine.it seemed to build rpm's really fast.makes sense,free flowing should spin up fast.
i made with a 90 degree elbow and a similar magnaflow muffler, my own exhaust.it has(seems to me) more down low power,and is a bit loud but seems to be getting quiet as it gets packed with carbon.
i examined a stock pipe inlet and outlet stuck into a can with no tubes to feed and direct the gases out.so i used the magnaflow (it has a perforated tube) for mine.the gases can let some of the pulses thru the perforated part and still have good flow till exit.
the old saying airflow is horsepower i tried to follow.all my old VW experience and other stuff too,air flow in the entire intake/exhaust needs to be free as can be of
restrictions and wierd bends.
do you plan to install that muffler into a stock can or use it underslung on it's own? that is how mine is.i have run it mostly with out the chin fairing as well.
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Johnboy777
Posted on Saturday, February 06, 2010 - 07:03 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Hey, Pogue_mahone,

That's a good idea, I had never thought of running that MagnaFlow inside a stock can.

I had this MagnaFlow system last year that was build by gbalias over on BuelletinBoard - at the time
I thought it might be a little much for the neighbors so I sold it. It was a great sounding system, though - like an old big block.

I keep the bike at my buddy's man cave now so I wanted to try another MagnaFlow.

I need a new elbow.

John



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